Phosphates were previously routinely included in detergents, including automatic dishwashing (ADW) detergents, due to their excellent chelating agent performance. Since use of phosphates in detergents is now limited or banned in most jurisdictions due to environmental concerns, a significant amount of research and development has been performed to identify and develop new and effective chelating agents, dispersants, and/or builders for ADW detergents having little or no phosphate in them. Polyacrylate dispersants are known to inhibit crystal growth and assist with particle dispersion. Amino carboxylates stoichiometrically bind metal ions, thereby enhancing scale inhibition, and are being explored as another class of chelants that may replace phosphates in detergents and other aqueous systems. Polyacrylate polymers which also contain amino carboxylate moieties have been found to be as effective as previously used builders and chelants such as phosphates, aminocarboxylates and polyacrylates containing sulfonate moieties. See, e.g., U.S. Patent Application Publication No. WO/2014/099237 (DOW74191/U.S. Ser. No. 61/739,262, filed Dec. 19, 2012; DOW75261/EP Patent Appln No. 13290210.7 filed Sep. 5, 2013), which describe polymers comprising polymerized units derived from carboxylic acid monomers, amino caboxylate monomers and glycidyl monomers that are useful as builders and chelants in automatic dishwashing detergents.
A family of patents which includes U.S. Pat. Nos. 4,906,383 and 4,913,880 described polymers useful for water treatment and derived from α-, β-ethylenically unsaturated monomers, which contain carboxylic acid or carboxylic amide functionalities, and amine-containing allyl ether monomers. These patents taught that the amine-containing allyl ether monomers were derived from the ring opening reaction of a (meth)allylic glycidyl ether, preferably allyl glycidyl ether (AGE), with ammonia, primary, secondary or tertiary amines, for example carboxylate-containing amines such as iminodiacetic acid (IDA). It was contemplated that these polymers, comprising both amine and carboxylic functionalities, would be useful in a broad range of water treatment applications including scale inhibition in water systems such as cooling, boiler, gas scrubbing, and pulp and paper manufacturing systems, as well as corrosion inhibitors and chelating activity for various metal ions in solution. It was further stated that such polymers may be used to prevent precipitation of various calcium-based fouling solids, as well as various metal oxide and metal hydroxide deposits, in water systems.
Moreover, polyacrylate polymers which contain sulfonic acid monomers, such as 2-acrylamido-2-methylpropane sulfonic acid (AMPS), are known to provide good inhibition against silica-based scale formation. Polymers commercially available under the tradename ACUSOL 588 from Dow Chemical Company contain acrylic acid and AMPS monomers and have been marketed for use in ADW detergents to control silica- and phosphorus-based scales. With the advent of phosphorus-free ADW detergents, ACUSOL 588 and similar dispersants remain effective at controlling silica-based scale.
Notwithstanding the foregoing developments, there remains a need for anti-scaling agents for ADW detergents to replace the now-disfavored phosphates that previously inhibited scale build-up.